Innovative Janus wood membranes: Harnessing wood anisotropy for superior liquid separation and transport

Abstract

The asymmetric wettability of Janus membranes shows promising prospects in the field of liquid transport and separation, and researchers are seeking environmentally friendly and cost-effective feedstock for fabricating these membranes. In this study, we developed two types of high-performance, flexible, and durable asymmetric Janus membranes from wood: Janus cross-section wood membrane (JCW) and Janus longitudinal-section wood membrane (JLW). Wood, being an anisotropic material stemming from its grain orientation, possesses a hierarchical porous structure that can be tailored for various practical applications. The JCW, characterized by its vertical wood channel structure and larger pore size, demonstrated superior unidirectional water transport and fog collection capabilities. Its water–oil separation efficiency reached 99.9 %, with a filtration flux exceeded 3000 L/m²∙h. The JLW, featuring three-dimensional interconnected micro-nano channels and layered pathways, was particularly effective in separating oil–water emulsions. The separation efficiency of oil–water emulsions reached 99.91 %, with filtration fluxes for water-in-oil and oil-in-water emulsions being as high as 500 and 700 L/m²∙h, respectively. These results underscored the potential of asymmetric wettability Janus membranes in the fields of liquid transport and separation, while also paving the way for the utilization of sustainable and eco-friendly feedstocks.